Overturning of single row pallet racks is a concern when the height-to-depth ratio is over 6 to 1. The Rack Manufacturers Institute defines the height-to-depth ratio for a single row of pallet rack to be the ratio of the distance from the floor to the top beam level divided by the depth of the frame. For example:
The height of the top beam level is 180 inches (15′), and the depth is 42 inches (3′ 6″). To determine the height-to depth ratio, divide 180 by 42 = 4.28. A ratio of 4.28 to 1 is considered within standard limits, and normal anchoring is used in a non-seismic application.
When the height-to-depth ratio exceeds 6 to 1, engineering should review the design to resist overturning. Special anchors, base plates and even overhead ties may need to be used.
Source: Rack Manufacturer’s Institute